This invention pertains generally to radio frequency energy antennas and more particularly to antennas adapted to produce electromagnetic beams over wide scan angles.
It has been suggested that a so-called "wide angle scanning array antenna" assembly, as described in U.S. Pat. No. 3,755,815, may be used when it is desired to deflect a radar beam through a deflection angle which may be greater, in any direction, than the maximum feasible deflection angle of a beam from a conventional planar phased array. Briefly, such an antenna assembly consists of a conventional planar phased array mounted within a structure which acts as a lens. When any portion of such structure is illuminated in a controlled fashion by a radar beam from the planar phased array, the direction of such radar beam with respect to the boresight line of the planar phased array is changed in a manner analogous to the way in which a prism bends visible light. Thus, the deflection angle of the radar beam propagated in free space may be caused to be much larger than the greatest deflection angle attainable with a planar phased array.
Although an assembly made in accordance with the disclosure of the cited patent is, in theory, suited to the purpose of deflecting a radar beam through extremely wide deflection angles, the beam is scanned by controlling the phase provided by each one of the phase shifters in the planar phased array, and hence the scan angle is frequency dependent, thereby limiting the bandwidth of the antenna.